Most Durable Finish Using Spray Cans

[M. Spencer]

I am about 15 pedals into this hobby and some friends are starting to ask me to build for them. My builds are pretty stable and the finishes are starting to look fairly respectable, but one drop and the paint starts chipping off. Apart from having an auto shop paint them or investing in a powder-coating setup, how do you get the most durable finish from a rattle can?

I am currently sanding the enclosure, washing it off with soap and water, using one or two coats of primer, three to five of color, then three coats of clear. Dry time is usually half hour to hour between coats.

Anyone have luck with the bake method making the paint more resistant to damage?

Thanks!  

[rocket88]

hey bro. i had the same thing for a long time, and this is what i do now.

here's my process:

1: i first coat the enclosure with a black sharpie marking and sand the enclosure to make it as flat as possible. this goes for whether or not i'm etching the enclosure. i wet sand up to 800 grit, starting at 320 grit, but in all honesty you can really stop at 400 grit, just force of habit to go to 800 for my brushed enclosures. the black sharpie lets me see where the low spots are. you don't need it to be completely flat, just a flat as i can without going too crazy.

2: wipe the entire enclosure down with acetone. i do this until i don't see any residue or discoloration. then i do it one more time just to be safe. this gets rid of any residue that can ruin the paint.

3: i move the enclosure to my painting area holding it with the acetone towel again, so that i don't get any fingerprints on it. once i set it down i leave it for 2-3min just to make sure the acetone evaporates.

4: i lay down my base coat thin, but so that the entire enclosure is a single uniform color. i move it to my baking pan, and place it in my special toaster oven for enclosures at roughly 150F for 30min. it's special only because it's only job is baking my enclosures, do NOT use one you'd use for food.

5: let it cool for 10min, then move it back to the paint area and do the same thing for 1-2 more coats, with each coat being baked and cooled.

6: i lay down the clear in a medium thickness coat and bake it. same process 150F for 30min, cool for 10min, and lay down a second coat.

i don't use a primer, even though i should, again, mostly because etch a lot of my enclosures and usually have a few places that end up as bare aluminum or it gets coated in a colored clear.

if you're going to use a primer, you should use an etching primer. it grabs onto the enclosure better making a good place for paint adhesion. if you do prime it, make sure you lightly sand it to make sure it's even and has some scratches for actual paint to grab onto. make sure you wipe it down to remove any contaminates. i follow similar steps to what i've done when i've done auto body work and so far i've had no issues.

what paint are you using? i use automotive paint, duplicolor to be exact.

[Beaker]

Yeah, Zach's method is a good one.

What I would say, is that paint has to have something to grip on to - if it can't grip, it will chip off very easily.

Ideally, bead blast the enclosure first,  then etch prime, then high build primer, then colour coat and finally clear coat.

Very few of us have access to a bead blaster, so scratch your enclosure up really  well with 60 or 80 grit paper - seriously, really go for it and scratch the crap out of it - and not just in one direction.

Wash it in soapy water, then dry and as Zach says, thoroughly clean with acetone.

Give it a very light mist coat with etch primer - it contains an acid that eats into and grips the metal.

Give it ten minutes to dry.

Then shoot a few coats of high build primer - this will fill in all the scratches and any pits in the enclosure.

Flat it off with wet paper - anything between 240 - 400 grit will do. You want a flat, smoth finish, but again, with enough "scratches" for the colour coat to grip to.

Thoroughly clean again with acetone, then colour coat - 3 or 4 coats.

If you have any runs or dust blemishes, carefully flat them off with wet 600 or 800 grit, then clean off with acetone. You can skip this part if your finish is good enough.

Finally give it 3 or 4 coats of clear coat. Wet flat again with 1000 or 1200 grit if neccessary.

Give it a polish if you want it to shine!


You only need to leave 10 to 15 minutes between coats at room temperature, 5  minutes if the enclosure is warmed.

I'm in two minds about the toaster ovens - some are far too hot at minimum temperature, and dry the paint too fast, which can lead to finish problems like crazing or solvent pop. And no, baking will not make the paint harder - it just means it hardens off quicker.

Having said that, when I finish my last clear coat, I stick the enclosure in my kitchen oven at about 50-60 degrees celsius for an hour or two. It saves leaving it for a week at room temperature to fully harden.

[M. Spencer]

I bought a dozen or so cans of Rust-oleum and Valspar - for indoor/outdoor, wood/metal. Next time I will try automotive spray and etch primer. I'd still like to use up what I bought before I get new colors, maybe with the acetone, sand-between-coats and wipe down steps they will hold up better. Hopefully...

I also roughed up the paint between coats with a scotchbrite pad, but something a little more fine sounds like it might provide better results for the paint to grip. I had been rough sanding with an attachment that fits on my hand drill using 80 grit (I think), so I will invest in some 300 - 600 wet sanding sand paper. (and youtube some techniques since I've never done wet sanding.)

Here I am trying to find ways to quicken the process when in reality to get better results it's gonna take me longer. Go figure, right? :)  

[Beaker]

Actually scotchbrite pads are absolutely ideal for keying up the surface between coats, so you are doing the right thing there. They are no good for flatting off runs though - that's where the block and paper comes in.

Wet sanding is really easy - soak the paper in water for ten minutes before use for best results, and use a flat  hard foam, rubber or cork sanding block and just sand as normal. The water forms a slurry that lubricates and really helps flatten the surface. Keep the paper nice and wet as you go. You can dry the paper and re-use it too - it lasts for ages if you wet sand.

Make sure you clean thoroughly after using any scotchbrite or abrasive paper.

Watch a few car paintwork re-finishing videos - the process is identical. Make sure you watch the pro ones though, as there are thousands of utterly crap ones on youtube, done by people who don't have clue!

But yes, you are right, you can't cut corners if you want good results. So it will take longer!